Multi-component pet food and method of manufacturing solid component

ABSTRACT

The invention concerns multi-component packaged food products which have been thermally processed to achieve commercial sterility in a package, including at least a first component and a second component in contact with (eg immersed in) the first component, wherein said first component is comprised of a substantially water-based, liquid, pasty or gelled food such as sauce, gel, gravy, jus or the like, and wherein the second component consists of one or more relatively hard, manufactured pieces that substantially retain their initial shape and hard or crunchy textural functionality for at least an expected shelf-life of the product whilst exposed to the moisture content of the first component.

FIELD OF THE INVENTION

The invention relates to the field of commercial pet food manufacture.In particular, the invention relates to an improved multi-component wetpackaged pet food product and a method for manufacturing a ‘non-wet’component for use in multi-component wet packaged pet food products.

The present patent application claims priority from Australianprovisional patent application 2010900089, the contents of itsspecification being hereby incorporated by way of cross-reference.

BACKGROUND OF THE INVENTION

Multi-component wet packaged food products have been marketed in mostmajor markets for decades, and are well known in particular also in thepet food manufacturing sector.

In the context of the present patent specification, the term‘multi-component’ is used to denote a product having a wet phase, orfirst food component, comprising as a major constituent water (but notexcluding other humectants) in which are dissolved or suspended otheredible substances, which is characterised by a high water activity oftypically above 85 to 90 and which at ambient temperature will typicallyhave a liquid, viscous or gelatinised consistency. Typicalrepresentatives of such wet phase components include gravies, jus, gels,sauces, etc. The multi-component product will also incorporate a second(or more) solid phase component that has separate and distinct physicalcharacteristics from the wet phase component and when immersed orotherwise in contact with the wet phase first component will keep to asubstantial extent its shape.

A further characteristic of ‘wet’ packaged foods is that they are madeshelf stable by heat treatment, e.g. retorted, canned, pouched orbottled foods, or hot-packed aseptically sealed products.

As an example, there are known canned pet food products in which ‘solid’constituents such as rice, real or ‘artificial meat’ (ie meat analogue)chunks and vegetable pieces are suspended in a syrupy (starchy) gravy,so that at lease two distinct textures are present at the time ofconsumption by the animal, whereby the shape-stable, distinct componentsremain separable from the gravy.

A consistent feature of these products is that the solid components tendto be relatively soft (ie chewy or resilient), whether they be meat orpoultry chunks, fish chunks, reformed meat chunks, vegetables, extrudedcereal-based or protein-based chunks and even pieces of vegetables whichare typically ‘hard’ in raw state, such as carrots. This is almostinevitable, given the heat conditions applied in making the foodcommercially sterile in the presence of water. Softening of theotherwise solid components also follows during shelf-life storage inthat these ‘take up’ moisture from the surrounding wet phase gel, gravyor the like. For the vast majority of these products, this is notnecessarily a problem, since such solid phase components are likely tobe reasonably palatable, and textural ‘shortcomings’ may not be tooproblematic, in particular upon consumption by a mammal pet.

However, there is an increasing trend to design food products, includingpet food, that carry specific health benefits by inclusion of ‘active’ingredients, such as nutraceutical or pharmaceutical actives, vitamins,minerals, amongst others. Unfortunately, many existing multi-componentfoods tend not to be useful for carrying and protecting many of saidactive ingredients during commercial sterilisation heat treatments, dueto their relatively high moisture levels. One way in which this problemhas been sought to be addressed in the past is by way ofmicro-encapsulation of active substances in heat and/or moistureresistant casings prior to embedding or infusion into manufactured meatanalogue chunks or suspension in the wet phase component.

Another aspect that is finding increasing attention in the pet foodindustry in particular, is a requirement for product differentiation byhaving multi-component foods which incorporate distinct texturescomponents, wherein a challenge remains in creating a packaged wetproduct with crunchy or crispy textural components that remain in suchtextural state within a liquid-based matrix during the shelf-life of theproduct.

Accordingly, it is one object of the present invention to provide amulti-component wet packaged food product, and a component therefor,that includes a component able to remain shape-stable and relatively‘hard’ or crunchy, to provide a point of textural variety, duringshelf-life of the product.

In another object, it would be beneficial for the relatively hard orcrunchy component to provide a suitable substrate for carryingsubstances to provide functional benefits to the consumer of the foodproduct.

Yet a further object is to provide a method of manufacturing acomestible, relatively hard or crunchy food component that will remainin such state when used in the manufacture of heat-treated, packaged wetfood products, in particular pet food products.

SUMMARY OF THE INVENTION

In one overarching aspect the invention resides in a multi-componentpackaged food product which has been thermally processed to achievecommercial sterility in a package, including at least a first componentand a second component in contact with (eg immersed in) the firstcomponent, wherein said first component is comprised of a substantiallywater-based, liquid, pasty or gelled food such as sauce, gel, gravy, jusor the like, and wherein the second component consists of one or morerelatively hard, manufactured pieces that substantially retain theirinitial shape and hard or crunchy textural functionality for at least anexpected shelf-life of the product whilst exposed to the moisturecontent of the first component.

According to a more specific aspect of the invention, there is provideda multi-component packaged food product which has been thermallyprocessed to achieve commercial sterility in said package, including atleast first and second components, wherein said first component consistsof a wet phase comprising water and other edible substances and having awater activity of above 85 and which at ambient temperature willtypically have a liquid; viscous or gelled consistency, and wherein saidsecond component comprises solid phase pieces at least partiallysurrounded by the first component and which have separate and distinctphysical characteristics from the wet phase component, characterised bythe solid phase pieces comprising a manufactured matrix of inorganic butedible mineral salts formed into a shape-stable object exhibiting a bulkwater activity value of 0.75 or below prior to thermal processing of thepackaged food product. In particular, the food product is a pet foodproduct.

The stable, low water activity of the solid phase pieces has advantagesin that these inclusions in a packaged wet pet food product are stablein the food product upon storage, and promote heat stability duringthermal processing of the multi-component food.

An advantage of such multi-component wet food product for pets is thatthe second component will maintain a relatively hard and crunchy texturethroughout the normal shelf-life of the food product, providing adifferent texture to that normally associated with ‘chunks in sauce’style products, which mammal pets tend to appreciate. Thistextural-stability within an aqueous environment which the wet phasecomponent represents may be leveraged to provide functional advantages,e.g. the use of particular shape profiles of the hard component piecesto promote good dental hygiene in pet animals.

Preferably, prior to thermal processing, the difference in wateractivity between said first component and said second component piecesis in the range 0.10 to 0.20, advantageously the gap is 0.15, the matrixof inorganic mineral salts ensuring that the pieces will keep to asubstantial extent their distinct shape when immersed or otherwise incontact with the wet phase first component. Preferably, said solidcomponent pieces have a bulk water activity of 0.70 or below prior tothermal processing, said first (ie wet phase) component has a wateractivity of 0.9 or above.

Preferably, the second component pieces comprise a matrix of calciummineral salts, most preferably a matrix of calcium hydroxyapatite(‘CHA’). This provides a relatively high degree of hardness (orcrunchiness) to the pieces which will be maintained following thermalprocessing in a relatively ‘wet’ environment. It is believed that CHAhas previously not been used in the manufacture of comestible foods,although it has been used in numerous other applications, as notedbelow.

Advantageously, the hard CHA matrix pieces will have an initial moisturecontent of less than 10.0% w/w prior to incorporation into the wet phasefirst component by immersion in it.

It should be noted that palatability of the relatively hard CHA matrixpieces is also an important aspect in the context of multi-component petfoods. Accordingly, palatant substances may advantageously beincorporated into the CHA matrix or onto the exterior surface of the CHAmatrix pieces, such as starches, sugars and generally palatantsubstances typically employed in the pet food manufacturing sector.

It has been surprisingly found that CHA matrix pieces formulated andmanufactured by dry blending of tri-calcium phosphate (TSP), calciumhydroxide (CH) and calcium sulphate (CS), subsequent addition of waterand appropriate tritration and neutralization (eg using a food-gradeacid such as diluted phosphoric acid) to an about neutral pH value,followed by optional conditioning of the resulting slurry prior todrying and form-shaping, will yield pieces which from a palatabilitypoint of view are better than the case where other precursor substancesare used in manufacturing the CHA. Accordingly, the above manufacturingprocess represents a further aspect of the present invention.

A preferred ratio of TSP:CH:CS is preferably in the range of 2:1:1,although this may be varied.

In yet a further aspect of the present invention, functional ingredientsare incorporated into the CHA matrix pieces prior to or after the pieceform-shaping step. These ingredients may include one or more materialsselected from the group comprising nutraceutical actives, pharmaceuticalactives, dentifrices and chelating agents.

Preferably, the second component pieces are formed by a process ofcompression, in particular compression tabletting. This technique, inparticular when using a CHA matrix formulation as previously described,provides a highly form or shape stable food component which retainsshape and low water activity when in contact with (or immersed in) wetphase components typically employed in the pet food industry, even afterundergoing cooking processes designed to produce commercial sterility.

It will be appreciated by those skilled in the art that the invention isof wide application in the field of commercial packaged foods, inparticular those intended for consumption by pets. Also, the inventionmay be applied to a number of food product formats, including chunks ingel, chunks in sauce, chunks in loaf, pieces in gravy, pieces in gel andpieces in loaf (wherein the piece can be any food piece). It would alsobe clear that the product may be packaged in any suitable foodcontainer, including steel cans, flexible aluminium or plastic trays,flexible pouches or sachets, glass bottles or jars, etc. These aspectsare known to the multi-component food formulator.

It would also be clear to the skilled addressee that the first componentmay be mingled or mixed with the second component either before or afterthermal processing of the second component, or mixed and mingled to bethermally processed together.

The invention also does not preclude the presence of third, fourth ormore other components. In other words, the present invention alsoforesees incorporation of solid phase pieces comprising a manufacturedmatrix of inorganic but edible mineral salts formed into a shape-stableobject exhibiting a bulk water activity value of 0.75 or below prior tothermal processing of the packaged food product, into an otherwise‘standard’ packaged wet food product having analogue meat pieces, meatchunks or other solids, as currently commercially available.

In the following, a detailed description will be provided on how tomanufacture solid phase components in accordance with one of the aspectsof the invention, for subsequent use in a multi-component wet packagedfood product.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the chemical structure of apatite in enamel, dentine andbone;

FIG. 2 shows the dissociation equilibrium equation for calciumhydroxyapatite in general terms;

FIG. 3 shows a flow diagram of a scaled-up manufacturing process inaccordance with one aspect of the present invention to yield a calciumhydroxyapatite which is preferably used in formulating hard componentpieces for use in a wet packaged food product;

FIG. 4 shows a graph illustrating the relative hardness values of solidfood component pieces in tablet form, which represent one aspect of thepresent invention, measured using a qualitative tablet screw test,wherein the shaded area depicts the perceived hardness value for theCHA-based tablet made in accordance with that aspect of the invention;and

FIG. 5 shows two photographs of CHA-based tablets according to theinvention, and their appearance in a wet food product after undergoing aretort cycle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Multi-component wet food products are know per se, and will thus not bedescribed further. Relevantly, different aspects of the inventioncomprise (i) how to manufacture and (ii) provide hard, manufacturedpieces that substantially retain their initial shape and hard or crunchytextural functionality for at least an expected shelf-life of suchmulti-component food product whilst exposed to the moisture content ofthe liquid, pasty or gelled, high water activity food component, as wellas (iii) a multi-component wet food product incorporating such hardpieces. Therefore, the following description will be limited to theseaspects.

There are numerous mineral compounds that may be used to manufacture arelatively hard and stable food piece for inclusion in a multi-componentfood product in accordance with the present invention. However, and inparticular, calcium salts are preferentially employed, both for theirstability and inherent texture, as well as for their contribution todietary calcium.

Calcium hydroxyapatite [CHA: Ca₁₀(PO₄)₆(OH)₂] has been identified as apreferred matrix material which can be used for such purpose.Consideration of the following factors led to such appreciation.

CHA is a major mineral component in animal and human bodies, especiallyin “load-bearing” tissues such as bone and teeth. For example, in atypical cortical bone, which is composed of: 22 wt % organic matrix, 69wt % mineral, 9 wt % water, the major sub-phase of the mineral componentconsists of sub-microscopic crystals of an apatite of calcium andphosphate. CHA is otherwise also an important inorganic material inbiology and chemistry. Biological apatites, which are the inorganicconstituents of bone, tooth enamel and dentin, however, are typicallyvery variable in their composition and morphology, and contain differentimpurities including: Mg²⁺, K⁺, Na⁺, CO₃ ⁻, HPO₄ ²⁻, Cl⁻, F⁻, andothers. In general, these impure biological apatites are designated ascalcium deficient or non-stoichiometric apatites.

FIG. 1 illustrates details on structure of different biologicalapatites.

Synthetic CHA, on the other hand, is also frequently used inbiomineralization and biomaterial studies. The composition,physicochemical properties, crystal size and morphology of syntheticapatites tend to be sensitive to preparative conditions. Common impurityphases in synthetic apatites prepared by precipitation fromsupersaturated aqueous solutions are calcium phosphate compounds such asamorphous calcium phosphates (ACP) with variable compositions ofCa₃(PO₄)_(2-2x)(HPO₄)_(3x).nH2O, octacalcium phosphate (OCP),Ca₈(HPO₄)₂(PO₄)₄.5H₂O, and calcium hydrogen phosphate dihydrate (DCPD),CaHPO₄.2H₂O. In addition, the incorporation of various ions as traceimpurities (hydrogen phosphate, carbonate, silicate ions, etc.) is verydifficult to prevent in any preparative procedure of CHA.

The most common reactions used for preparation of CHA in the literatureare:

Consequently, and having regard to the manufacturing process dependentshortcomings mentioned above, CHA may be used in formulatingfood-compatible components that may impart a different texturalsensation when mingled, embedded or otherwise present in amulti-component wet food product.

In this context, one has to take account of the fact that the moistureand pH of the wet food component in which CHA-based hard food componentpieces would be incorporated greatly influences the stability of the CHAmaterial. The dissociation equilibrium equation for calciumhydroxyapatite is shown in FIG. 2.

On dissociation, hydroxyapatite produces two ions, phosphate andhydroxyl, capable of accepting protons. Hydroxyapatite is, therefore, aweak base. Phosphate is capable of accepting three protons and has threepossible pK values: 12.3, 7.2 and 2.1. As the pH of the aqueous phasedrops, the ratio of the concentrations of the various forms of phosphatechanges as more and more phosphate is progressively protonated.Similarly, as the pH drops, hydroxyl ions are protonated and the [OH]ion concentration reduces.

Knowledge of the relationship between pH and pK allows prediction of thebehaviour of the phosphate and relation of this to mineral dissolution.At near neutral pH, say pH 7.2, the ratio of mono- and di-hydrogenphosphate can be calculated, which means that when the pH of thesolution is equal to the pK, the concentration of mono- and di-hydrogenphosphate is the same. Similar calculations can be applied to the otherpK values but these are a long way outside the physiological values ofpH which are experienced in vivo or in a food matrix.

It is interesting to calculate the ratio of phosphate ion tomono-hydrogen phosphate at near neutral pH because it is theconcentration of the un-protonated phosphate, together with hydroxylion, which affects the dissociation of CHA.

Against this background, some key points as to the suitability of usingCHA in the manufacture of a food component are summarised below:

-   -   The dissociation constant (pK) defines the ratio of the        concentrations of the dissociated ions and the undissociated        acid.    -   The Henderson-Hasselbach equation relates pK, pH and the ratio        of salt concentration to un-dissociated acid. The buffering        action of any weak acid-salt mixture is at its greatest close to        the pK of the weak acid. Phosphate can accept three protons and        has three possible pK values, 12.3, 7.2 and 2.1.    -   In the dissociation of hydroxyapatite, it is the concentration        of non-protonated phosphate and hydroxyl ions which are        important. As the pH becomes more acid, more phosphate is        protonated resulting in the dissolution of more mineral.    -   In food, it is important to consider buffering capacity of        proteins present in a food matrix. Moisture in food and its        saturation with respect to calcium and phosphate and the        presence of other salts/ions can greatly impact on the stability        of CHA dental active material.    -   Calcium phosphate-based biomaterials have been in use in        medicine and dentistry for over 20 years because of their        excellent biocompatibility with human tissues, e.g. dental        implants, percutaneous devices, periodontal treatment, alveolar        ridge augmentation, orthopaedics, maxillofacial surgery,        otolaryngology, and spinal surgery.    -   Hydroxyapatite is also currently used for fractionation and        purification of a wide variety of biological molecules, such as        subclasses of enzymes, antibody fragments, and nucleic acids.

Having established the suitability of using CHA in formulating a foodcomponent that may be used in a multi-component wet food product, thechallenge was then to identify and provide a process for the manufactureof CHA that is physiologically acceptable and which material may then beused to provide a substrate for or mayor constituent of a texturallyhard or crunchy food piece.

In accordance with one aspect of the invention, such process wasdevised. It comprises the steps of mixing suitable CHA-precursoringredients, titrating with water and a suitable food-grade acid toachieve an adequately neutralised slurry, and subjecting the slurrythrough various conditioning, maturing and drying steps, some of whichare optional, to obtain a material which can then be form-shaped intofood pieces, either alone or in combination with other constituents.

A process flow diagram for manufacturing a preferred food-grade CHA isillustrated in FIG. 3, using exemplary process parameter values andquantities of ingredients as determined suitable from pilot scale tests.

This process involves the dry blending of (3 Kg) tri-calcium phosphate(TCP), (1.5 Kg) calcium hydroxide (CH) and (1.5 Kg) calcium sulphate(CS). This is best performed using a rotary drum mixer as it was foundto yield optimum mixing/blending of the dry ingredients as compared withother mixers, such as a pin-mixer. The dry blended ingredients are thenplaced into a Hobart mixer, and a sufficient quantity of water is addedto make a thick slurry. The slurry is slowly neutralized by the additionof acid (80% phosphoric acid diluted 1:1 with water) with continuousstirring/mixing. The pH of the starting slurry was >12.0 and had asandy/gritty texture, whereas the resulting titrated material slurryexhibits a smooth ‘plaster-like’ texture with a neutral pH value ofaround 7.0; total weight of the aqueous slurry at this stage set to 12Kg.

The neutralized (titrated) slurry material is then subjected to anoptional conditioning stage in suitable conditioning vessels. Suitableconditioning parameters are 75° C. at 100% relative humidity for threehrs. An optional maturation stage may then include resting theconditioned material at room temperature (23° C.) for no less than 12hrs, preferably 24 hrs, before the material is fully dried at 80° C. forsuch time as to achieve a dry product with preferably not more than 10%w/w moisture content.

This dried CHA material can then be granulated or pulverized andsubsequently form-shaped into discrete pieces.

A preferred form-shaping process resides in direct dry compressiontabletting of the CHA, either alone or with a small w/w % of addedconstituents such as palatants and tabletting aid agents (eg Mg Sterate)to form a water repellent though not entirely water impervious outersurface and to a compression degree sufficient to have a shape-stableobject that can be handled during food product manufacturing operationswithout breaking up. The specific shape of the pieces is not limiting,as is the weight, although typical tablet sizes and lenticular shapessuch as encountered in the pharmaceutical industry provide guidance inachieving form-stable pieces.

For CHA-matrix, hard tabletted pieces to be successfully incorporatedinto multi-component wet (pet) food products, whereby these maintainshape integrity and textural quality within the multi-component product,these must meet requirements for crunch and crisp wet metrics for suchproducts in the marketplace.

To determine this, CHA tablets were manufactured using slight variationsof the above general formula/recipe and compressed to different degreesto establish adequate compression values (and formulations) required forsuch tabletted CHA-matrix pieces to maintain adequate ‘crunchiness’ (orhardness) over the intended shelf-life in a multi-component wet pet foodproduct.

The relative hardness of the solid pieces is tested after tabletting,prior to inclusion into the multi-component wet food product, as well asafter retort processing of the multi-component food product to a degreewhich achieves commercial sterility. It will be appreciated that thedegree of ‘crunchiness’ that will be present at the end or past theshelf-life will depend to some, although small degree, also on theactual water activity of the specific liquid food component in which thehard CHA-matrix pieces are immersed. Also, being a relative sensoryvalue, it is not possible to provide a preferred formulistic orvalue-specific hardness, softness or crunchiness indicator. The‘softness’ and ‘hardness’ of CHA-matrix tablets is thus better indicatedon a qualitative (yet ultimately arbitrary) hardness scale, such asillustrated in FIG. 4. It would seem from tests carried out that mediumrelative hardness values, as depicted by the highlighted area in FIG. 4,should be aimed for when using the CHA-formulated tablets as per theinvention.

CHA materials produced were typically also more suitable for tablettingwhen they had been dried further (towards a lower w/w % moisturecontent) and pre-granulated (rather than pulverised).

FIG. 8, left hand side, illustrates actually manufactured CHA-matrixtablets having a medium relative hardness, according to the recipe notedabove, whilst the right hand side of FIG. 8 shows a commercial ‘meatchunks in gravy’ food product, which includes soft or chewy foodcomponents in a gravy as well as a number of solid and crunchy tablets,after being retorted. This photo shows that the tablets maintain theirshape-integrity and have not been disintegrated or substantiallysoftened as consequence of retorting in an aqueous environment.Subsequent to shelf-life storage, the multi-component food productshowed almost unchanged characteristics, ie in the finishedmulti-component food product, the shape integrity of the hard tablettedpieces was maintained and the textural quality met the requirements forcrunch and for crisp wet metrics required for such products in themarketplace.

1. A multi-component packaged food product which has been thermallyprocessed to achieve commercial sterility in a package, including atleast a first component and a second component in contact with (egimmersed in) the first component, wherein said first component iscomprised of a substantially water-based, liquid, pasty or gelled foodsuch as sauce, gel, gravy, jus and the like, and wherein the secondcomponent consists of one or more relatively hard, manufactured piecesthat substantially retain an initial shape and crunchy texturalfunctionality for at least an expected shelf-life of the product whilstexposed to the moisture content of the first component.
 2. Amulti-component packaged food product which has been thermally processedto achieve commercial sterility in a package, including at least firstand second components, wherein said first component consists of a wetphase comprising water and other edible substances and having a wateractivity of above 85 and which at ambient temperature will typicallyhave a liquid, viscous or gelled consistency, and wherein said secondcomponent comprises solid phase pieces at least partially surrounded bythe first component and which have separate and distinct physicalcharacteristics from the wet phase component, characterised by the solidphase pieces comprising a manufactured matrix of inorganic but ediblemineral salts formed into a shape-stable object exhibiting a bulk wateractivity value of 0.75 or below prior to thermal processing of thepackaged food product.
 3. The multi-component packaged food product ofclaim 1, wherein the second component pieces have an initial moisturecontent of less than 10.0% w/w prior to incorporation into said firstcomponent.
 4. The multi-component packaged food product of claim 1,wherein prior to thermal processing, the difference in water activitybetween said first component and said second component pieces is in therange 0.10 to 0.20.
 5. The multi-component packaged food product ofclaim 1, wherein the first component has a water activity of at least0.9.
 6. The multi-component packaged food product of claim 1, whereinthe second component solid phase pieces are substantially formed by aprocess of compression.
 7. The multi-component packaged food product ofclaim 1, wherein the second component pieces comprise a matrix ofinorganic material, preferably including calcium mineral salts, and morepreferably a matrix comprised of calcium hydroxyapatite.
 8. Themulti-component packaged food product of claim 7, wherein one or morematerials selected from the group consisting of nutraceutical actives,pharmaceutical actives, vitamins, functional minerals, dentifrices andchelating agents are incorporated into the calcium hydroxyapatitepieces.
 9. The multi-component packaged food product of claim 7, whereinpalatant substances such as food starches, sugars and the like areincorporated into the pieces or are present on the tabletted calciumhydroxyapatite pieces.
 10. The multi-component packaged food product ofclaim 7, wherein the calcium hydroxyapatite is formulated andmanufactured by dry blending of tri-calcium phosphate (TCP), calciumhydroxide (CH) and calcium sulphate (CS), preferably in a ratio of about2TCP:1CH:1CS, subsequent addition of water and appropriate tritrationand neutralization using a food-grade acid to an about neutral pH value,followed by optional conditioning of the resulting slurry prior todrying and granulating.
 11. A food piece for incorporation in athermally processed multi-component wet packaged food product, said foodpiece being formed substantially from a matrix of calcium mineral salt,preferably calcium hydroxyapatite.
 12. The food piece of claim 11,having a moisture content of less than 10.0% w/w prior to incorporationin the food product.
 13. The food piece of claim 11, additionallyincorporating one or more materials selected from the group consistingof nutraceutical actives, pharmaceutical actives, vitamins, functionalminerals, dentifrices, chelating agents and food palatants.
 14. The foodpiece of claim 11, wherein the food piece is substantially formed by aprocess of compression tabletting.
 15. (canceled)
 16. (canceled)
 17. Amethod of manufacturing a hard pet food piece for inclusion as acomponent in a packaged multi-component wet pet food product, comprisingthe steps of dry blending of tri-calcium phosphate (TSP), calciumhydroxide (CH) and calcium sulphate (CS), subsequent addition of waterand appropriate titration and neutralization using a food-grade acid, toan about neutral pH value, followed by optional conditioning andmaturing of the resulting slurry at specified temperature conditions andfor a predetermined time, followed by drying and form-shaping into acrunchy piece having a moisture content no greater than 10% w/w.
 18. Themulti-component packaged food product of claim 2, wherein the secondcomponent pieces have an initial moisture content of less than 10.0% w/wprior to incorporation into said first component.
 19. Themulti-component packaged food product of claim 2, wherein prior tothermal processing, the difference in water activity between said firstcomponent and said second component pieces is in the range 0.10 to 0.20.20. The multi-component packaged food product of claim 2, wherein thefirst component has a water activity of at least 0.9.
 21. Themulti-component packaged food product of claim 2, wherein the secondcomponent solid phase pieces are substantially formed by a process ofcompression.
 22. The multi-component packaged food product of claim 2,wherein the second component pieces comprise a matrix of inorganicmaterial, preferably including calcium mineral salts, and morepreferably a matrix comprised of calcium hydroxyapatite.
 23. Themulti-component packaged food product of claim 22, wherein one or morematerials selected from the group consisting of nutraceutical actives,pharmaceutical actives, vitamins, functional minerals, dentifrices andchelating agents are incorporated into the calcium hydroxyapatitepieces.
 24. The multi-component packaged food product of claim 22,wherein palatant substances such as food starches, sugars and the likeare incorporated into the pieces or are present on the tabletted calciumhydroxyapatite pieces.
 25. The multi-component packaged food product ofclaim 22, wherein the calcium hydroxyapatite is formulated andmanufactured by dry blending of tri-calcium phosphate (TCP), calciumhydroxide (CH) and calcium sulphate (CS), preferably in a ratio of about2TCP:1CH:1CS, subsequent addition of water and appropriate tritrationand neutralization using a food-grade acid to an about neutral pH value,followed by optional conditioning of the resulting slurry prior todrying and granulating.